Rotating fluid machine

ABSTRACT

An expander includes a rotor rotatably supported by a casing, a group of axial pistons and cylinders installed so that its axis is surrounded by the rotor, and a swash plate having a rotating surface inclined with respect to the axis of the rotor and is rotatably supported by the casing. The relative rotation of the swash plate and the rotor around the axis is restricted and the relative shifting of the swash plate and rotor in the direction of the axis is allowed, by fitting a slider, fixed to the swash plate by a synchro-pin, into a long hole of an output shaft. Therefore, it is possible to prevent wrenching between the swash plate and the rotor due to thermal expansion while reducing the bending moment acting on the pistons of the group of axial pistons and cylinders of the expander.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a rotating fluid machine which performs conversion between pressure energy and mechanical energy of a working medium via a group of axial pistons and cylinders, and a swash plate.

[0003] 2. Description of the Related Art

[0004] Such rotating fluid machines are publicly known through Japanese Patent Laid-Open No. 2002-256805 and Japanese Patent Laid-Open No. 50-100406. The one described in Japanese Patent Laid-Open No. 2002-256805 is provided with a first group of axial pistons and cylinders arranged inside in the radial direction and a second group of axial pistons and cylinders arranged outside in the radial direction; the spherical heads of the pistons of the first group of axial pistons and cylinders are in contact with dimples formed in the swash plate, and the pistons of the second group of axial pistons and cylinders are linked to the swash plate by connecting rods. The phase of a rotor supporting the first and second groups of axial pistons and cylinders and that of the swash plate are kept the same by the contact between the spherical heads of the pistons of the first group of axial pistons and cylinders and the dimples in the swash plate.

[0005] In Japanese Patent Laid-Open No. 50-100406, the pistons of the first group of axial pistons and cylinders arranged in a casing and a swash plate rotatably supported by the output shaft are linked by connecting rods, and the phase of the casing and that of the swash plate are kept the same by the meshing of gears provided on both.

[0006] Also, in Japanese Patent Laid-Open No. 2002-256805, the phases of the rotor and the swash plate are maintained to be the same by placing the spherical heads of the pistons of the first group of axial pistons and cylinders in contact with the dimples in the swash plate, so that the bending moment applied by the swash plate to the pistons may invite the occurrence of wrenching between the pistons and cylinder sleeves, leading to abnormal wear. Especially in an expander using high temperature high pressure steam as the working medium, since water resulting from the condensation of steam inevitably becomes mixed with oil, the lubricating conditions between the pistons and the cylinder sleeves may deteriorate to aggravate abnormal wear.

[0007] In Japanese Patent Laid-Open No. 50-100406, as the pistons and the swash plate are linked by the connecting rods, no bending moment is applied by the swash plate to the pistons. However, as the phases of the casing and the swash plate are maintained to be the same by engaging the gears provided on these two elements, if there is a difference in the amount of thermal expansion in the axial direction between the output shaft supporting the swash plate and the casing, the engagement between the gears may deteriorate to invite the occurrence of wrenching.

[0008] Further, in the case where the pistons of a group of axial pistons and cylinders are connected to the swash plate by connecting rods, if the diameter of the swash plate is increased to extend the stroke of the pistons, the inclination of the connecting rods relative to the axis of the rotor will increase; especially in the early stage of the expansion stroke in which the reactive load applied by the swash plate to the pistons via the connecting rods is greater, the load in the radial direction pressing the outer circumferential faces of the pistons against the inner circumferential faces of the cylinder sleeves increases, so that abnormal wear or seizure due to wrenching may arise. In order to avoid this problem, if the diameter of the swash plate is reduced to decrease the inclination of the connecting rods relative to the rotor, the stroke of the pistons will become shorter, entailing a possible drop in the output of the rotating fluid machine.

SUMMARY OF THE INVENTION

[0009] The present invention has been achieved in view of the circumstances stated above, and it is a first object of the present invention to prevent wrenching between the swash plate and the rotor due to thermal expansion while reducing the bending moment acting on the pistons of a group of axial pistons and cylinders.

[0010] A second object of the invention is to prevent abnormal wear and seizure by reducing the load acting in the radial direction on the pistons while increasing the diameter of swash plate to extend the piston stroke.

[0011] In order to achieve the first object stated above, according to a first characteristic of the invention, there is proposed a rotating fluid machine comprising a rotor supported rotatably by a casing, a group of axial pistons and cylinders disposed on the rotor so as to surround its axis, a swash plate having a rotating surface inclined relative to the axis of the rotor and is supported rotatably by the casing, connecting rods for linking the pistons of the group of axial pistons and cylinders to the swash plate, and linking means for linking the swash plate to the rotor, wherein said linking means restricts the rotation of the swash plate and the rotor relative to each other around the axis and permits the movements of the swash plate and the rotor relative to each other in the axial direction.

[0012] According to the configuration described above, since the pistons of the group of axial pistons and cylinders and the swash plate of the rotating fluid machine are linked by the connecting rods, and the linking means linking the swash plate to the rotor restricts the rotation of the swash plate and the rotor relative to each other around the axis, it is possible to minimize the bending moment which the pistons receive due to a reactive force from the swash plate, to thereby avoid wrenching of the sliding faces of the pistons and the cylinders to prevent abnormal wear, and at the same time to reduce the frictional forces of the sliding faces to enhance the efficiency of the rotating fluid machine. Moreover, because of use of the connecting rods, the rotating fluid machine can be made more compact to reduce the size of the pistons in the axial direction, and the required strength of the pistons can be reduced to reduce the weight of the rotating fluid machine. Aat the same time, the efficiency of the rotating fluid machine can be enhanced by reducing the escape of heat through the pistons. Furthermore, as the linking means permits the swash plate and the rotor to move relative to each other in the axial direction, relative movements of the swash plate and rotor in the axial direction due to thermal expansion can be absorbed to facilitate smooth operation of the rotating fluid machine.

[0013] According to a second characteristic of the invention there is proposed a rotating fluid machine wherein, in addition to the first characteristic stated above, said linking means is arranged within the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and is orthogonal to the axis of the swash plate.

[0014] According to the configuration described above, as the linking means is arranged within the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and which is orthogonal to the axis of the swash plate, the torque of the swash plate can be smoothly transmitted to the rotor by preventing any uneven load from acting between the swash plate and the rotor.

[0015] According to a third characteristic of the invention, there is proposed a rotating fluid machine wherein, in addition to the first or second characteristic stated above, wherein a plurality of the linking means are arranged.

[0016] According to the configuration described above, as a plurality of the linking means are arranged, the load can be distributed among those linking means to improve the durability of the linking means.

[0017] According to a fourth characteristic of the invention, there is proposed a rotating fluid machine wherein, in addition to the third characteristic stated above, the plurality of linking means are radially arranged within the rotating surface of the swash plate which is orthogonal to the axis of the swash plate.

[0018] According to the configuration described above, as the plurality of linking means are radially arranged within the rotating surface of the swash plate which is orthogonal to the axis of the swash plate, the phasic difference between the swash plate and the rotor can be effectively reduced further enhance the effect of suppressing vibration.

[0019] According to a fifth characteristic of the invention, there is proposed a rotating fluid machine wherein, in addition to the first characteristic stated above, pivotal portions of the connecting rods on the swash plate side are offset by a prescribed distance toward the piston side of the swash plate in the axial direction with respect to the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and is orthogonal to the axis of the swash plate.

[0020] According to the configuration described above, as the pivotal portions of the connecting rods on the swash plate side are offset by a prescribed distance toward the piston side of the swash plate in the axial direction with respect to the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and is orthogonal to the axis of the swash plate, it is made possible to minimize the inclination of the pistons at the top dead center with respect to the connecting rods and the axis of the rotor while increasing the stroke of the pistons by extending the diameter of the swash plate, to reduce the component of the reactive force in the radial direction acting from the swash plate on the pistons via the connecting rods, and thereby to prevent the occurrence of abnormal wear or seizure.

[0021] In order to achieve the second object stated above, according to a sixth characteristic of the invention, there is proposed a rotating fluid machine comprising a rotor supported rotatably by a casing, a group of axial pistons and cylinders disposed on the rotor so as to surround its axis, a swash plate having an axis inclined relative to the axis of the rotor and is supported rotatably by the casing, connecting rods for linking the pistons of the group of axial pistons and cylinders to the swash plate via pivotal portions of the pistons, and linking means for linking the swash plate to the rotor, wherein the pivotal portions of the connecting rods on the swash plate side are offset by a prescribed distance toward the piston side of the swash plate in the axial direction with respect to the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and is orthogonal to the axis of the swash plate.

[0022] In the configuration described above, as the pivotal portions of the connecting rods for linking the pistons of the group of axial pistons and cylinders of the rotating fluid machine to the swash plate on the swash plate side are offset by a prescribed distance toward the piston side of the swash plate in the axial direction with respect to the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and is orthogonal to the axis of the swash plate, it is made possible to minimize the inclination of the pistons at the top dead center with respect to the connecting rods and the axis of the rotor while extending the stroke of the pistons by increasing the diameter of the swash plate, to reduce the component of the reactive force in the radial direction acting from the swash plate on the pistons via the connecting rods, and thereby to prevent the occurrence of abnormal wear or seizure.

[0023] Incidentally, a long hole 32 e, a slider 47 and a synchro-pin 46 in the embodiment corresponding to the linking means according to the invention, and spherical parts 45 a and 45 b in the embodiment corresponding to the pivotal portions according to the invention.

[0024] The aforementioned and other objects, features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments thereof when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is a vertical sectional view of an expander according to a first embodiment of the invention.

[0026]FIG. 2 is an enlarged view taken on line 2-2 in FIG. 1.

[0027]FIG. 3 is an enlarged view of Part 3 in FIG. 1.

[0028]FIG. 4 is an exploded perspective view of a rotor and a swash plate.

[0029]FIG. 5 is a sectional view taken on line 5-5 in FIG. 3.

[0030]FIG. 6 is a sectional view taken on line 6-6 in FIG. 3.

[0031]FIG. 7 is a sectional view taken on line 7-7 in FIG. 3.

[0032]FIG. 8 is a view taken from arrow 8 in FIG. 3.

[0033]FIG. 9 is a view corresponding to FIG. 8 and explaining the operation.

[0034]FIG. 10 is a vertical sectional view of an expander according to a second embodiment of the invention.

[0035]FIG. 11 is an enlarged view of Part 11 in FIG. 10.

[0036]FIG. 12 is a sectional view taken on line 12-12 in FIG. 11.

[0037]FIG. 13 is a view for explaining the inclination of connecting rods accompanying the rotation of a rotor.

[0038]FIG. 14A through FIG. 14C are views for explaining the effect of the offset of the spherical parts of the connecting rods on the swash plate side.

[0039]FIG. 15 is a graph showing the phasic difference between the rotor and the swash plate where the rotor and the swash plate are coupled with a single synchro-pin.

[0040]FIG. 17 is a graph showing the phasic difference between the rotor and the swash plate with respect to five synchro-pins differing in phase by 72° each.

[0041]FIG. 18 is a view showing the locus of the synchro-pin shifting within a long groove along with phasic variations of the rotor.

[0042]FIG. 19A through FIG. 19E are views showing the positional relationship between the synchro-pin and the long groove varying along with phasic variations of the rotor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] A first preferred embodiment of the present invention will be described below with reference to FIG. 1 through FIG. 9.

[0044] As shown in FIG. 1 through FIG. 7, an expander E according to the first embodiment of the present invention, which is for use in, for instance, a Rankine cycle system, converts thermal energy and pressure energy of high temperature high pressure steam as a working medium into mechanical energy, and outputs the converted energy. The casing 11 of the expander E is configured of a casing body 12, a front cover 15 fitted to the front opening of the casing body 12 with a plurality of bolts 14 . . . with a sealing member 13 therebetween, a rear cover 18 fitted to the rear opening of the casing body 12 with a plurality of bolts 17 . . . with a sealing member 16 therebetween, and an oil pan 21 fitted to the bottom opening of the casing body 12 with a plurality of bolts 20 . . . with a sealing member 19 therebetween.

[0045] A rotor 22 arranged to be rotatable around an axis L extending in the middle of the casing 11 in the back and forth directions is supported in front by combined angular bearings 23 f and 23 r disposed on the front cover 15 and on the back by a radial bearing 24 disposed on the casing body 12. Integrally formed on the rear face of the front cover 15 is a swash plate holder 28. A swash plate 31 is rotatably supported by this swash plate holder 28 via a radial bearing 29 and a thrust bearing 30. The axis of the swash plate 31 is inclined relative to the axis L of the rotor 22, and the angle of its inclination is fixed.

[0046] The rotor 22 is provided with an output shaft 32 supported on the front cover 15 with the combined angular bearings 23 f and 23 r, a rotor body 33 formed integrally with the rear part of the output shaft 32, and a rotor head 36 connected to the rear face of the rotor body 33 with a plurality of bolts 35 . . . with a metal gasket 34 therebetween and supported on the casing body 12 by the radial bearing 24.

[0047] Five sleeve supporting holes 33 a . . . are bored in the rotor body 33 around the axis L at 72° intervals, and five cylinder sleeves 37 . . . are fitted into those sleeve supporting holes 33 a . . . from behind. Formed at the rear end of each of the cylinder sleeves 37 is a flange 37 a, which is positioned in the axial direction in contact with the metal gasket 34 in a state in which it is fitted onto a stepped portion 33 b formed in the sleeve supporting hole 33 a of the rotor body 33 (see FIG. 3). A piston 38 is slidably fitted in each of the cylinder sleeves 37. Two compression rings 39 and 39 and one oil ring 40 are supported on the outer circumference of the piston 38. A steam expansion chamber 42 is partitioned among the metal gasket 34, an annular lid member 41 jointed to a rotor head 36 and a top face of the piston 38.

[0048] A connecting rod holder 43 is fitted within each of the pistons 38 on and engaged with a clip 44. A spherical part 45 a at the rear end of each connecting rod 45 is oscillatably linked to the connecting rod holder 43, and a spherical part 45 b at the front end oscillatably linked to the swash plate 31.

[0049] The five cylinder sleeves 37 . . . and the five pistons 38 . . . constitute a group 55 of axial pistons and cylinders.

[0050] A long hole 32 e extending in the direction of the axis L penetrates, in the radial direction, the rear part of the output shaft 32 near the rotor body 33. A round opening 31 a penetrates the center of the swash plate 31 in the direction of the axis L, and pin holes 31 b and 31 c crossing the opening 31 a are bored in the radial direction. One pin hole 31 b penetrates the outer circumferential face of the swash plate 31 from the opening 31 a, and the other pin hole 31 c is made a blind hole directed from the opening 31 a toward the outer circumferential face of the swash plate 31 to avoid interference with the spherical parts 45 b at the front ends of the connecting rods 45. A flange 46 a is formed at one end of a synchro-pin 46 to be inserted from the one pin hole 31 b to the other pin hole 31 c, and a concave 31 d into which this flange 46 a is to be fitted is formed in the outer circumferential face of the swash plate 31 so as to surround the one pin hole 31 b.

[0051] A cylindrical slider 47 having two parallel faces 47 a and 47 a is fitted in the radial direction onto the inner circumference of the opening 31 a of the swash plate 31, and the penetration into its inside by the synchro-pin 46 causes the slider 47 to be fixed to the swash plate 31. The synchro-pin 46 is fixed to the swash plate 31 by the press fitting of a spring pin 48. As the two end faces 47 b and 47 b of the slider 47 are formed of parts of a spherical face having its center in the middle part of the slider 47 in its lengthwise direction, the occurrence of wrenching can be prevented and smooth assembly facilitated when fitting it into the opening 31 a of the swash plate 31.

[0052] Two parallel cuts 46 b and 46 b are formed on the flange 46 a of the synchro-pin 46 and, in a state in which the synchro-pin 46 is fixed by the spring pin 48, one of the cuts 46 b of the flange 46 a to be fitted onto the concave 31 d is flush with the rear end face 31 e of the swash plate 31 (see FIG. 8). To pull the synchro-pin 46 out of the pin holes 31 b and 31 c, the spring pin 48 is removed, and then the flange 46 a is turned about 90° in the concave 31 d. As a result, part of the flange 46 a will protrude from the rear end face 31 e of the swash plate 31, and then the synchro-pin 46 can be easily pulled out while holding that protruding portion with fingers (see FIG. 9).

[0053] A planar bearing holder 92 is laid over the front face of the front cover 15 with a sealing member 91 therebetween and fixed with bolts 93 . . . , and the pump body 95 of an oil pump 49 is laid over the front face of that bearing holder 92 with a sealing member 94 therebetween and fixed with bolts 96 . . . The combined angular bearings 23 f and 23 r, positioned between the stepped portion of the front cover 15 and the bearing holder 92, are fixed in the direction of the axis L.

[0054] A shim 97 of a prescribed thickness is placed between a flange 32 d (see FIG. 3) formed in the output shaft 32 and the inner races of the combined angular bearings 23 f and 23 r, and the inner races of the combined angular bearings 23 f and 23 r are fastened with nuts 98 screwed onto the outer circumference of the output shaft 32. As a result, the output shaft 32 is positioned in the direction of the axis L relative to the combined angular bearings 23 f and 23 r, namely with respect to the casing 11.

[0055] The combined angular bearings 23 f and 23 r are fitted in mutually reverse orientations, and support the output shaft 32 not only in the radial direction but also immovably in the direction of the axis L. Thus, one combined angular bearing 23 f is so arranged as to restrict the forward movement of the output shaft 32, while the other combined angular bearing 23 r is arranged to restrict the backward movement of the output shaft 32.

[0056] As the combined angular bearings 23 f and 23 r are used for bearing the fore part of the rotor 22, one of the loads generated in the expansion chambers 42 . . . to act on the two ends of the axis L in a prescribed operating state of the expander E is transmitted via the rotor 22 to the inner races of the combined angular bearings 23 f and 23 r, and the other load is transmitted via the swash plate 31 and the swash plate holder 28 of the front cover 15 to the outer races of the combined angular bearings 23 f and 23 r. These two loads compress the swash plate holder 28 of the front cover 15 held between the thrust bearing 30 supporting the swash plate 31 and the combined angular bearings 23 f and 23 r supporting the rotor 22, resulting in enhanced rigidity of the mechanism. Moreover, the integral configuration of the swash plate holder 28 with the front cover 15 as in this embodiment of the invention makes the structure even more rigid and simpler.

[0057] Further, by incorporating the radial bearing 29 and the thrust bearing 30 supporting the swash plate 31 and the combined angular bearings 23 f and 23 r supporting the rotor 22 into the front cover 15, it is possible to perform the assembling for the units of “the rotor 22 and the piston 38 . . . ”, “assembly of the front cover 15” and “the pump body 95”, to thereby improve the efficiency of tasks such as rearrangement of the piston 38 . . . and the replacement of the oil pump 49.

[0058] The radial bearing 24 supporting the rotor head 36 which constitutes the rear end of the rotor 22 is an ordinary ball bearing supporting only the load in the radial direction, a gap α is formed between the rotor head 36 and the inner race of the radial bearing 24 (see FIG. 1) so that the rotor head 36 can slide in the direction of the axis L relative to the radial bearing 24.

[0059] An oil passage 32 a extending on the axis L is formed within the output shaft 32 integrated with the rotor 22, and the inner circumference of the rear end of this oil passage 32 a is blocked by an oil passage blocking member 61. The front end of the oil passage 32 a branches in radial directions to communicate with an annular groove 32 b of the outer circumference of the output shaft 32, and the middle part of the oil passage 32 a, in its portion communicating with the long hole 32 e, is blocked by two sealing members 62 and 63. Further, the front and rear parts of the oil passage 32 a communicate with each other via the oil passage 32 f, and at the same time the oil passage 32 a on the rear side communicates with an the annular groove 33 c . . . formed in the sleeve supporting hole 33 a via oil holes 32 c . . . extending in the radial direction. The annular grooves 33 c . . . and the outer circumferential faces of the pistons 38 communicate with each other via oil holes 37 b . . . penetrating the cylinder sleeves 37 . . .

[0060] A trochoidal oil pump 49 arranged between a concave 95 a formed in the front face of the pump body 95 and a pump cover 58 fixed with a plurality of bolts 57 . . . to the front face of the pump body 95 with a sealing member 56 therebetween, is provided with an outer rotor 50 rotatably fitted into the concave 95 a, and an inner rotor 51 fixed to the outer circumference of the output shaft 32 to engage with the outer rotor 50. The inner space of the oil pan 21 communicates with the intake port 53 of the oil pump 49 via an oil pipe 52 and the oil passage 95 b of the pump body 95, and the discharge port 54 of the oil pump 49 communicates with the annular groove 32 b of the output shaft 32 via the oil passage 95 c of the pump body 95.

[0061] A rotary valve 64 for supplying and discharging steam to and from five expansion chambers 42 . . . of the rotor 22 is arranged behind the rotor 22 on the axis L. The rotary valve 64 is provided with a valve body 65, a stationary valve plate 66 and a moving valve plate 67. The moving valve plate 67, in a state in which it is positioned in the rotating direction on the rear face of the rotor 22 with a knock pin 68, is fixed with a bolt 69 screwed onto the oil passage blocking member 61. The stationary valve plate 66 in contact with the moving valve plate 67 via a flat sliding faces 70 is formed integrally with the valve body 65, and the valve body 65 is engaged by a knock pin 71 with the rear cover 18 to be movable in the direction of the axis L and immovable in the rotational direction. The stationary valve plate 66 and the moving valve plate 67 are tightly adhered to each other on the sliding faces 70 by pressing forward the valve body 65 relative to the rear cover 18 with a plurality of preload springs 72 . . . so as to surround the axis L. Then a steam feed pipe 73 is connected to the rear face of the valve body 65.

[0062] Next will be described the operation of the expander E in the first embodiment of the invention configured as described above.

[0063] High temperature high pressure steam generated by heating water in an evaporator flows from the steam feed pipe 73, and reaches the sliding face 70 of the moving valve plate 67 via a steam passage formed in the valve body 65 of the rotary valve 64 and the stationary valve plate 66. The steam passage opening in the sliding face 70 momentarily communicates for a prescribed air intake period with a matching steam passage formed in the moving valve plate 67 turning integrally with the rotor 22, and the high temperature high pressure steam is supplied to the expansion chamber 42 within the cylinder sleeve 37 from the steam passage of the moving valve plate 67.

[0064] Even after the steam supply to the expansion chamber 42 is cut off along with the rotation of the rotor 22, expansion of high temperature high pressure steam in the expansion chamber 42 causes the piston 38 fitted into the cylinder sleeve 37 to be thrust forward from the top dead center to the bottom dead center, and the connecting rod 45 connected to the piston 38 presses the swash plate 31. As a result, the reaction force from the swash plate holder 28 gives a rotational torque to the swash plate 31, and that rotational torque is transmitted to the output shaft 32 via the long hole 32 e from the slider 47 fitted onto the outer circumference of the synchro-pin 46 fixed to the swash plate 31, causing the output shaft 32 to turn together with the rotor 22. Every time the rotor 22 turns a ⅕ round, high temperature high pressure steam is supplied to the adjoining new expansion chamber 43 to drive the rotor 22 for continuous rotation.

[0065] While the piston 38 having reached the bottom dead center along with the rotation of the rotor 22 is pushed by the swash plate 31 to recede toward the top dead center, low temperature low pressure steam thrust out of the expansion chamber 42 is discharged to a condenser via the moving valve plate 67 integrated with the rotor 22, the sliding faces 70, the stationary valve plate 66 and the valve body 65.

[0066] The oil pump 49 provided on the output shaft 32 is actuated along with the rotation of the rotor 22, oil sucked from the oil pan 21 via the oil pipe 52, the oil passage 95 b of the pump body 95 and the intake port 53 is discharged from the discharge port 54, and is supplied via the oil passage 95 c of the pump body 95, the annular groove 32 b of the output shaft 32, the oil passages 32 a, 32 f and 32 a of the output shaft 32, the oil holes 32 c . . . of the output shaft 32, the annular groove 33 c . . . of the rotor body 33, and the oil holes 37 b of the cylinder sleeves 37 to the sliding faces between the pistons 38 . . . and the cylinder sleeves 37 . . . to lubricate those sliding faces.

[0067] When the thrust in the direction of the axis L generated by the pistons 38 . . . of the group of axial pistons and cylinders 55 is converted via the swash plate 31 into the rotational force of the rotor 22, as the pistons 38 . . . are not brought into direct contact with the swash plate 31 but the pistons 38 . . . are linked to the swash plate 31 via the connecting rods 45 . . . , the bending moment caused to work on the pistons 38 . . . by a reaction force from the swash plate 31 can be minimized. Thus, even if water resulting from the condensation of high temperature high pressure steam becomes mixed with oil to deteriorate the lubricating conditions, it is possible to avert wrenching of the sliding faces between the pistons 38 . . . and the cylinder sleeves 37 . . . to prevent abnormal wear from occurring and to reduce the frictional force of the sliding faces to increase the efficiency of the expander E. Moreover, as the bending moment of the pistons 38 . . . is minimized, it is possible to reduce the size of the expander E by shortening the dimension of the pistons 38 . . . in the direction of the axis L and to lighten the weight by reducing the required strength of the pistons 38 . . . Furthermore, as the heat mass is reduced as a result of the decrease in the size of the pistons 38 . . . , it is possible to enhance the efficiency of the expander E by reducing the escape of heat through the pistons 38 . . .

[0068] As the slider 47 supported by the synchro-pin 46 is slidably fitted into the long hole 32 e of the output shaft 32, the swash plate 31 and the rotor 22 are allowed to move in the direction of the axis L in a relative manner, and it is possible to absorb any difference in the quantity of thermal expansion in the direction of the axis L between the rotor 22 and the casing 11 to enable the expander E to operate smoothly. Further, as the two parallel faces 47 a and 47 a of the slider 47 supported by the synchro-pin 46 are brought into face contact with the long hole 32 e without fitting the synchro-pin 46 directly into the long hole 32 e, the wear of its sliding portion is minimized to thereby prevent chattering.

[0069] Incidentally, when assembling the expander E, the magnitude of the dead volume between the bottom of the cylinder sleeves 37 (i.e. the rotor head 36 to which the lid member 41 is jointed) and the top of the pistons 38, namely the volume of the expansion chambers 42 when the pistons 38 are at the top dead center, has to be adjusted. If the shim 97 intervening between the flange 32 d of the output shaft 32 and the inner races of the combined angular bearings 23 f and 23 r is thinned, the output shaft 32 will shift forward (rightward in FIG. 1) and accordingly the rotor head 36 will also shift forward, but as the pistons 38 cannot move forward because of the restriction by the swash plate 31, the dead volume will decrease. Conversely, if the shim 97 is thickened, the rotor head 36 will move backward (leftward in FIG. 1) together with the output shaft 32, and accordingly the dead volume will increase. As a result, it is possible to adjust the dead volume as desired by merely replacing the shim 97, and the step otherwise needed for dead volume adjustment can be eliminated to achieve a substantial saving of time.

[0070] Further, as it is possible adjust the dead volume only by sandwiching a single shim 97 having a prescribed thickness between the flange 32 d of the output shaft 32 and the combined angular bearings 23 f and 23 r and fastening, with a single nut 98, the front cover 15 incorporating the radial bearing 29, the thrust bearing 30 and the combined angular bearings 23 f and 23 r and the rotor 22 incorporating the pistons 38 . . . , the adjusting task is simplified as compared with the conventional adjustment process in which the thicknesses of two shims, front and rear, are individually manipulated. Moreover, since the rotor 22 incorporating the pistons 38 . . . can be kept assembled into the casing body 12 when adjusting the dead volume, the adjusted dead volume can be confirmed by directly watching the state of contact between the pistons 38 . . . and the swash plate 31.

[0071] When the position of the output shaft 32 relative to the combined angular bearings 23 f and 23 r is adjusted back and forth by varying the thickness of the shim 97 as described above, the position of the rotor head 36 at the rear end of the rotor 22 also shifts back and forth, but there is no trouble in adjusting the position of the output shaft 32 because the rotor head 36 is slidable in the direction of the axis L relative to the inner race of the radial bearing 24 disposed between it and the casing body 12, and the long hole 32 e bored in the output shaft 32 can slide in the direction of the axis L relative to the slider 47 provided on the swash plate 31.

[0072] Then, when the pressure of high temperature high pressure steam supplied to the expansion chambers 42 presses the pistons 38 in the direction of being thrust out of the cylinder sleeves 37, the pressing force of the pistons 38 presses forward (rightward in FIG. 1) the outer race of the combined angular bearings 23 f and 23 r via the connecting rods 45, the swash plate 31, the thrust bearing 30, the swash plate holder 28 and the front cover 15, and the pressing force of the cylinder sleeves 37 reverse in direction to the pressing force of the pistons 38 presses backward (leftward in FIG. 1) the inner race of the combined angular bearings 23 f and 23 r via the rotor head 36 and the output shaft 32. Thus, the load generated by the high temperature high pressure steam supplied to the expansion chambers 42 is cancelled within the combined angular bearings 23 f and 23 r, but not transmitted to the casing body 12.

[0073] While the rotor 22 composed of the output shaft 32, the rotor body 33 and the rotor head 36 is formed of a ferrous material whose thermal expansion is relatively small, the casing 11 which supports the rotor 22 via the combined angular bearings 23 f and 23 r and the radial bearing 24 is formed of an aluminum-based material whose thermal expansion is relatively large; as a consequence, there arises a difference in the quantity of thermal expansion especially in the direction along the axis L depending on whether the temperature of the expander E is high or low.

[0074] The casing 11, which is greater in thermal expansion than the rotor 22, expands more than the rotor 22 when the temperature is high, with its dimension in the direction of the axis L relatively increasing; conversely, when the temperature is low, it contracts more, with its dimension in the direction of the axis L relatively decreasing. As the casing 11 and the rotor 22 are positioned in the direction of the axis L via the combined angular bearings 23 f and 23 r, the difference in the quantity of thermal expansion between them is absorbed by the sliding contact of the rotor head 36 with the inner race of the radial bearing 24, and an excessive load is prevented from acting in the direction of the axis L on the combined angular bearings 23 f and 23 r, the radial bearing 24 and the rotor 22. This not only contributes to improvement of the durability of the combined angular bearings 23 f and 23 r and of the radial bearing 24, but also to stabilized support of the rotor 22 to facilitate its smooth rotation, and moreover to the prevention of fluctuations in dead volume between the bottom of the cylinder sleeves 37 (i.e. the rotor head 36 to which the lid member 41 is jointed) and the top of the pistons 38 accompanying variations in temperature.

[0075] The reason is that, supposing that both ends of the rotor 22 are restrained by the casing 11 to be immovable in the axial direction, as the casing 11 tends to contract in the direction of the axis L relative to the rotor 22 when the temperature is low, the pistons 38 whose top is in contact with the swash plate 31 supported by the swash plate holder 28, which is part of the casing 11, are pressed backward, and the rotor head 36 supported by the casing 11 via the radial bearing 24 is pressed forward, with the result that the pistons 38 are pressed into the cylinder sleeves 37 and the dead volume decreases accordingly. Conversely, when the temperature is high, as the casing 11 tends to expand in the direction of the axis L relative to the rotor 22, the pistons 38 are drawn out from the inside of the cylinder sleeves 37, resulting in an increase in dead volume, which in turn invites an increase in the initial volume of high temperature high pressure steam in the normal operating state after the warming-up, i.e. a drop in thermal efficiency due to a decrease in the volume ratio (expansion ratio) of the expander E.

[0076] By contrast in this embodiment of the invention, as the rotor 22 is supported in a floating state in the direction of the axis L relative to the casing 11, the gaps between the combined angular bearings 23 f and 23 r and the radial bearing 24 are prevented from widening and thus the preloads are prevented from decreasing, so that the dead volume is kept from fluctuations due to temperature variations. This prevents the volume ratio (expansion ratio) of the expander E from fluctuating, so that stable performance to be achieved.

[0077] Especially, in the expander E which uses high temperature high pressure steam as the working medium, the above-described advantage is highly effective because the difference is wide between high and low temperatures. Furthermore, whereas the difference between high and low temperatures is particularly wide in the vicinity of the rotary valve 64 to which high temperature high pressure steam is supplied, the difference in thermal expansion between the casing 11 and the rotor 22 can be absorbed without trouble because the rotor head 36 can slide in the direction of the axis L relative to the radial bearing 24 arranged closer to that rotary valve 64.

[0078] Next will be described a second preferred embodiment of the present invention with reference to FIG. 10 through FIG. 19E. Incidentally, in the second embodiments, members having counterparts in the first embodiment are denoted by respectively the same signs to dispense with duplicated description.

[0079] As shown in FIG. 10 through FIG. 12, the rotor 22 is provided with the output shaft 32 supported by the combined angular bearings 23 f and 23 r to the front cover 15, a spherical member 26 fitted onto the outer circumference of the output shaft 32 and fixed with a knock pin 25, the rotor body 33 formed integrally with the rear part of the output shaft 32, and the rotor head 36 coupled to the rear face the rotor body 33 by the plurality of bolts 35 . . . with the metal gasket 34 therebetween and supported in the casing body 12 by the radial bearing 24. The connecting rod holder 43 is fitted within the pistons 38 and engaged by the clip 44, and the spherical parts 45 a at the rear end of the connecting rods 45 are oscillatably linked to the connecting rod holder 43 while the spherical parts 45 b at the front end are oscillatably linked to the swash plate 31. Then a cover member 76 is fixed to the rear face of the swash plate 31 with a plurality of bolts 27 . . . , and the spherical parts 45 b at the frond ends of the connecting rods 45 are prevented by this cover member 76 from coming off.

[0080] Five long grooves 26 a . . . extending in the direction of the axis L are formed at 72° intervals in the spherical member 26 fixed to the outer circumference of the output shaft 32 and, by screwing a male thread 77 a into the inner circumferential face of the opening 31 a of the annularly shaped swash plate 31 or by spigot-fitting, the heads 77 b . . . of five synchro-pins 77 . . . radially fixed at 72° intervals are loosely fitted into the respectively matching long grooves 26 a . . . Therefore, the rotational torque of the swash plate 31 is transmitted from the long groove 26 a . . . fitted onto the outer circumference of the heads 77 b . . . of the five synchro-pins 77 . . . to the output shaft 32 via the spherical member 26, and causes the output shaft 32 to turn together with the rotor 22.

[0081] As well illustrated in FIG. 12, while the width of each of the long grooves 26 a of the spherical member 26 is constant in the radial direction around the axis L, the heads 77 b of the synchro-pins 77 loosely fitted into the long grooves 26 a are tapered at an angle of 2° so as to become thinner toward the outside in the radial direction. Therefore, when the output shaft 32 and the swash plate 31 have slightly turned relative to each other, the heads 77 b of the synchro-pins 77 come into linear contact with the inner faces of the long grooves 26 a, and the resultant drop in the surface stress of the contact portions makes it possible to suppress wear. The five synchro-pins 77 . . . are arranged between the five connecting rods 45 . . . , and this arrangement serves to effectively avoid interference between the synchro-pins 77 . . . and the connecting rods 45 . . .

[0082] As shown in detail in FIG. 11 and FIG. 13, the axis L of the rotor 22 and the axis Ls of the swash plate 31 cross each other at an intersection point C, and the spherical parts 45 b . . . of the five connecting rods 45 . . . toward the swash plate 31 side are offset by a prescribed distance δ toward the pistons 38 . . . from the rotating surface Ps of the swash plate passing the intersection point C (a plane orthogonal to the axis Ls of the swash plate 31). While this offset causes the spherical parts 45 b . . . of the connecting rods 45 . . . to be displaced toward the swash plate 31 side to deviate downward in FIG. 11, the quantity of offset is set so that the connecting rods 45 linked to the pistons 38 at the top dead center (the pistons 38 shown in the upper part of FIG. 11) is substantially parallel to the axis L of the rotor 22. Therefore, when the pistons 38 are at the top dead center, the connecting rods 45 are substantially parallel to the axis L of the rotor 22, and while they move from the top dead center to the bottom dead center and return to the top dead center again, the connecting rods 45 are inclined with respect to the axis L of the rotor 22.

[0083] Further, as the five synchro-pins 77 . . . are arranged on the rotating surface Ps of the swash plate, it is possible to prevent any uneven load from occurring when the torque of the swash plate 31 is transmitted to the spherical member 26, to thereby facilitate smooth torque transmission.

[0084] The oil passage 32 a extending on the axis L is formed within the output shaft 32 integrated with the rotor 22, and the inner circumference of the rear end of this oil passage 32 a is blocked by the oil passage blocking member 61. The front end of the oil passage 32 a branches in radial directions to communicate with the annular groove 32 b on the outer circumference of the output shaft 32, the middle part of the oil passage 32 a communicates with the oil holes 32 g . . . extending in radial directions, and further the rear end of the oil passage 32 a communicates with the annular groove 33 c . . . cut in the sleeve supporting holes 33 a . . . via the oil holes 32 c . . . extending in radial directions. The annular grooves 33 c . . . and the outer circumference of the pistons 38 communicate with each other via the oil holes 37 b . . . penetrating the cylinder sleeves 37 . . . , and the oil holes 32 g . . . communicate with the inner faces of the long grooves 26 a . . . via oil holes 26 b . . . bored in a spherical member 26. Therefore, oil in the oil passage 32 a of the output shaft 32 is supplied to the long grooves 26 a . . . via the oil holes 32 g of the output shaft 32 and the oil holes 26 b . . . of the spherical member 26, and lubricates the sliding faces of the long grooves 26 a . . . and the heads 77 b of the synchro-pins 77.

[0085] Next will be described the operation of the expander E in the second embodiment of the invention configured as described above.

[0086] When the pistons 38 are near the top dead center, i.e. in their suction stroke, high temperature high pressure steam is supplied to the expansion chambers 42 to thrust the pistons 38 forward under the maximum load, and the reaction force from the swash plate 31 strongly acts on the pistons 38 via the connecting rods 45, as the connecting rods 45 are substantially parallel to the axis L of the rotor 22, it is possible to minimize the load acting in the radial direction on the sliding faces of the pistons 38 and the cylinder sleeves 37, to prevent wrenching or abnormal wear from occurring on the sliding faces and reduce frictional resistance, to thereby contribute to increasing the output of the expander E.

[0087] Although the angle of inclination of the connecting rods 45 with respect to the axis L of the rotor 22 becomes greater in the final phase of the expansion stroke or the exhaust stroke, there is no fear of the occurrence of wrenching or abnormal wear on the sliding faces of the pistons 38 and the cylinder sleeves 37, because the reactive load acting from the swash plate 31 on the pistons 38 via the connecting rods 45 becomes smaller.

[0088] As described above, even though it is attempted to boost the output of the expander E by expanding the diameter of the swash plate 31 to elongate the stroke of the pistons 38 . . . , the center of the spherical parts 45 b . . . is projected in the direction of the axis L of the rotor 22 by offsetting the spherical parts 45 b . . . of the connecting rods 45 . . . toward the pistons 38 side by a prescribed distance δ relative to the rotating surface Ps of the swash plate, its locus will constitute an oval orbit whose center is offset toward the bottom dead center by δ·sin α, so that it is possible to narrow the angle of inclination of the connecting rods 45 of the pistons 38 near the top dead center to reduce the frictional resistance of the sliding faces of the pistons 38 . . . and the cylinder sleeves 37 . . . (see FIG. 14A).

[0089] By contrast, as shown in FIG. 14C, if the diameter of the swash plate 31 is merely expanded, the angle of inclination of the connecting rods 45 linked to the pistons 38 at the top dead center will widen to invite an increase in the frictional resistance of the sliding faces of the pistons 38 and the cylinder sleeves 37; or if the diameter of the swash plate 31 is shortened as shown in FIG. 14B, though the angle of inclination of the connecting rods 45 will narrow, the stroke of the pistons 38 will decrease, resulting in a drop in the output of the expander E.

[0090]FIG. 15 shows the phasic difference between the rotor 22 and the swash plate 31 in a supposed case in which the rotor 22 and the swash plate 31 are coupled by a single synchro-pin. In this case, as the axis L of the rotor 22 and the axis Ls of the swash plate 31 are inclined, the single synchro-pin constitutes a non-constant velocity joint and, even if the rotor 22 turns at a constant angular velocity, the angular velocity of the swash plate 31 will vary. For this reason, the phase of the rotor 22 and that of the swash plate 31 become different along with the rotation of the rotor 22.

[0091] For instance, if the phase of the rotor 22 and that of the swash plate 31 are identical at 0° when #1 piston 38 is at the top dead center in FIG. 15, the phasic difference between the rotor 22 and the swash plate 31 will vary over two cycles in a sine wave shape while the rotor 22 makes a single turn. Therefore, when #2 piston 38 has reached the top dead center, the phasic difference will be approximately +1°; when #3 piston 38 has reached the top dead center, the phasic difference will be approximately −2°; when #4 piston 38 has reached the top dead center, the phasic difference will be approximately +2°; and when #5 piston 38 has reached the top dead center, the phasic difference will be approximately −2°.

[0092] If in this way the phasic difference between the rotor 22 and the swash plate 31 varies from one piston 38 to another, the volumes of the expansion chambers 42 will vary with the phasic difference between the rotor 22 and the swash plate 31, and accordingly the expansion ratio of high temperature high pressure steam will differ from one expansion chamber 42 to another; therefore, even if the optimal suction timing or exhaust timing is set for a specific expansion chamber 42, the timing will not be optimal for other expansion chambers 42. The difference in output from one set of cylinder sleeve 37 and piston 38 to another would give rise to a problem of occurrence of a low order (first or second rotation) vibration.

[0093] In this embodiment of the invention, however, by arranging the five synchro-pins 77 . . . at equal intervals in the circumferential direction and causing the five synchro-pins 77 . . . to function sequentially along with the rotation of the rotor 22, the phasic difference between the rotor 22 and the swash plate 31 can be made uniform for every piston 38, and the problem noted above can be thereby solved. The reason for this solution will be further explained below.

[0094] The five sine waves shown in FIG. 16 represent variations in the phasic differences between the rotor 22 and the swash plate 31, in the case where the phasic difference between the rotor 22 and the swash plate 31 is set to be 0° when #1 piston 38 through #5 piston 38 are at their respective top dead centers. Where there is only one synchro-pin 77, the phasic difference varies within a range of ±2°, but the successive suppression by the five synchro-pins 77 . . . arranged at 72° intervals of phasic differences occurring between the rotor 22 and the swash plate 31 results in substantially constant phasic differences of around +2° as indicated by bold solid lines in FIG. 17; it is thus possible to increase the output of the expander E and to suppress vibration by setting uniform and optimal suction timing and exhaust timing for every one of the five expansion chambers 42 . . .

[0095]FIG. 18 and FIG. 19A through FIG. 19E illustrate how a synchro-pin 77 travels within the long grooves 26 a of the spherical member 26 of the output shaft 32; the black synchro-pins 77 in FIG. 19A through FIG. 19E represent the same synchro-pin 77 shifting along with the rotation of the rotor 22. When the synchro-pin 77 is at the top dead center of phase 0° (see FIG. 19A), that synchro-pin 77 is in the central position (1) of the long groove 26 a in the widthwise direction (the rotational direction of the rotor 22). When the rotor 22 has turned to the position of phase 45° (see FIG. 19B), the synchro-pin 77 travels within the long grooves 26 a in the direction of the axis L forward in the rotational direction of the rotor 22, and comes into contact with position (2) on one side of the long groove 26 a. In this state, torque is transmitted from the swash plate 31 to the rotor 22 via the synchro-pin 77.

[0096] When the rotor 22 has rotated to the position of phase 90° (see FIG. 19C), the synchro-pin 77 shifts toward the delayed side in the rotational direction of the rotor 22 while traveling within the long grooves 26 a in the direction of the axis L, and returns to the central position (3) in the widthwise direction of the long groove 26 a; when the rotor 22 has further rotated to the position of phase 135° (see FIG. 19D), the synchro-pin 77 shifts toward the delayed side in the rotational direction of the rotor 22 while traveling within the long grooves 26 a in the direction of the axis L, and comes into contact with position (4) on another side of the long groove 26 a, where the other side of the long grooves 26 a is on the delayed side in the rotational direction of the rotor 22, and accordingly the synchro-pin 77 does not contribute to torque transmission from the swash plate 31 to the rotor 22. When the rotor 22 has rotated to the position of phase 180° (see FIG. 19E), the synchro-pin 77 shifts toward the advanced side in the rotational direction of the rotor 22 while traveling within the long groove 26 a in the direction of the axis L, and returns to the central position (5) in the widthwise direction of the long grooves 26 a.

[0097] When the rotor 22 rotates in the latter half from phase 180° to phase 360° , the synchro-pin 77, as represented by a chain line in FIG. 18, shifts within the long groove 26 a in the reverse direction to that in the former half from phase 0° to phase 180° described above. In this process, the synchro-pin 77 comes into contact with one side of the long groove 26 a toward the advanced side of the rotational direction in the position of phase 225° (i.e. position (6)). In this state, the torque of the rotor 22 is transmitted from the swash plate 31 via the synchro-pin 77. Incidentally, parenthesized numerals (1) through (9) in FIG. 18 respectively corresponds to parenthesized numerals (1) through (9) in FIG. 15.

[0098] Thus, the installation of the five synchro-pins 77 makes possible continuous torque transmission from the swash plate 31 to the rotor 22 because the five synchro-pins 77 sequentially come into contact with one side of the long grooves 26 a on the advanced side of the rotational direction twice during a single turn of the rotor 22. Since the timing of this torque transmission is performed in the position of phase 45° and the position of phase 225° from the top dead center for every synchro-pin 77, the five pistons 38 can contribute to even driving of the rotor 22.

[0099] Where the number of synchro-pins 77 . . . is n (n is a natural number not smaller than 2), phase variations of the 2n-th order will occur during a single turn of the rotor 22, and the greater the value n, the shorter the cycle of vibration, thereby greatly contributing to the suppression of vibration. Moreover, as the number of the synchro-pins 77 . . . increases, the load on each synchro-pin 77 decreases, thereby enhancing its durability. Especially, the arrangement of the five synchro-pins 77 . . . at equal intervals makes it possible to effectively reduce phasic differences between the rotor 22 and the swash plate 31, and at the same time to further enhance the effect to suppress vibration.

[0100] While the preferred embodiments of the present invention have been described above, the invention can be modified in design in various ways without deviating from the subject matter.

[0101] For instance, the rotating fluid machine according to the invention is not limited to the expander E using compressive fluid as the working medium, but can as well be a compressor using compressive fluid as the working medium, a hydraulic pump or a motor using non-compressive fluid as the working medium.

[0102] Further, although the second embodiment is provided with five synchro-pins 77, the number of the synchro-pins 77 . . . can be appropriately varied only if it is more than one, and the greater their number, the more effectively the phasic difference can be reduced.

[0103] Also, although the heads 77 b of the synchro-pins 77 in the second embodiment have a circular section, they may have a rectangular or oval section. The use of a rectangular section would bring the heads of the synchro-pins 77 into face contact with the long grooves 26 a, making it possible to further enhance their durability. 

1. A rotating fluid machine comprising a rotor supported rotatably by a casing, a group of axial pistons and cylinders disposed on the rotor so as to surround its axis, a swash plate having a rotating surface inclined relative to the axis of the rotor and is supported rotatably by the casing, connecting rods for linking the pistons of the group of axial pistons and cylinders to the swash plate, and linking means for linking the swash plate to the rotor, wherein said linking means restricts the rotation of the swash plate and the rotor relative to each other around the axis and permits the movements of the swash plate and the rotor relative to each other in the axial direction.
 2. The rotating fluid machine according to claim 1, wherein said linking means is arranged within the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and is orthogonal to the axis of the swash plate.
 3. The rotating fluid machine according to claim 1, wherein a plurality of said linking means are arranged.
 4. The rotating fluid machine according to claim 3, wherein said plurality of linking means are radially arranged within the rotating surface of the swash plate which is orthogonal to the axis of the swash plate.
 5. The rotating fluid machine according to claim 1, wherein pivotal portions of the connecting rods on the swash plate side are offset by a prescribed distance toward the piston side of the swash plate in the axial direction with respect to the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and is orthogonal to the axis of the swash plate.
 6. A rotating fluid machine comprising a rotor supported rotatably by a casing, a group of axial pistons and cylinders disposed on the rotor so as to surround its axis, a swash plate having an axis inclined relative to the axis of the rotor and is supported rotatably by the casing, connecting rods for linking the pistons of the group of axial pistons and cylinders to the swash plate via pivotal portions of the pistons, and linking means for linking the swash plate to the rotor, wherein the pivotal portions of the connecting rods on the swash plate side are offset by a prescribed distance toward the piston side of the swash plate in the axial direction with respect to the rotating surface of the swash plate which passes the intersection point between the axis of the rotor and the axis of the swash plate and is orthogonal to the axis of the swash plate. 